CHAPTER 4 SEWING MACHINE REPAIR

The Aircrew Survival Equipmentman (PR) is called upon to perform an enormous amount of repair work on parachutes and survival equipment in all types of maintenance activities. Although lower rated personnel perform much of this work, the task of maintaining the sewing machines in top running condition falls to the senior PRs. Qualified sewing machine operators may assist in this work under supervision; however, determining the causes of malfunctions, making major adjustments, and replacing parts are the responsibilities of the first class and chief petty officer.

This chapter explains the rotory-hook (111 W 155) sewing machine and the oscillating-shuttle (31-15) sewing machine. We gave you an overview of these two types of sewing machines in chapter 3 of the Aircrew Survival Equipmentman 3 & 2, volume 1; however, as a senior PR, you need more specific information on the basic structure of these two sewing machines. With the information available, you can repair any of these types of machines the Navy uses. We know it is very difficult to find information on sewing machine repair; therefore, you should use this chapter as a reference when working on the alternating-presser-foot sewing machine and the simple oscillating-shuttle sewing machine.

Your shop may have the Consew Model 225, the Juki LU-562, or the Singer Model 111 W 155 sewing machine. These three sewing machines are essentially identical, and all specifications and instructions are the same for all three sewing machines. For simplicity we will use the Singer 111 W 155 as a model for all three sewing machines.

The oscillating-shuttle, Singer 31-15, sewing machine is representative of the second type of sewing machine used by the Navy. The descriptive term oscillating shuttle refers to the action of the sewing hook (the way it makes a stitch in unison with the needle). The 31-15 is used for sewing lightweight fabrics and is ideally suited for use in the maintenance of aviation survival equipment. Although the physical size of other oscillating-shuttle sewing machines may be quite different from the 31-15, such as the large Class 7 machines, their operation and maintenance are very similar.

111 W 155 SEWING MACHINE

The 111 W 155 sewing machine is a single-needle, compound-feed sewing machine with alternating presser feet. This sewing machine makes the standard US 301 lockstitch and sews medium-heavy fabrics. It is equipped with a vertical-axis rotating hook. This sewing machine is classified as a rotory-type sewing machine and is also equipped with two presser feet; one is a vibrating presser foot, and the other one is a lifting presser foot. The front (vibrating) presser foot, the needle, and the feed dogs move in unison. Together they move the cloth away from the operator with each completed stitch. The rear (lifting) presser foot holds the fabric in place while the vibrating presser foot rises and moves forward to start the feeding action for another stitch. This sewing machine is capable of operating at a speed of 3500 stitches per minute (SPM). The stitch regulator provides a range of 3 1/2 to 32 stitches per inch (SPI).

The 111 W 155 is the same sewing machine in most ways as the 111 W 151, except for its alternating presser feet, which give the 111 W 155 a more positive feeding action. The 111 W 155 also has a longer stitch length (3 1/2 SPI instead of 5 SPI) and a higher maximum presser-foot lift (one-half inch instead of three-eighths inch). The 111 W 155 is an ideal sewing machine to use on medium-heavy fabrics such as vinyl and canvas.

This RTM will also include disassembly and assembly of the 111 W 155 sewing machine. To simplify minor repairs to this sewing machine and the 31-15 sewing machine, we have placed our discussion of disassembly and assembly to the rear of the chapter.